The embodiments herein relate generally to a loudspeaker system and more specifically to a co-axial speaker system for generating enhanced sound by reducing the distortion of wave propagation using a generally flat diaphragm and generally flat suspension. The invention described may be applied to speakers that are not co-axial in nature, however.
The creation of robust hi-fidelity audio not only involves the science of carefully integrating an array of technologies for electronic to acoustic transformation, but also the art of passionately fine-tuning those integrated technologies within an optimized form factor to enrich the acoustic sound into an experience that is astounding to discerning audiophiles and inspiring to all. As such, modern loudspeakers have evolved over the years into truly enviable works of art and science. The invention described herein reflects the passion of combining art and science in a way that enhances the experience even more than what has been produced heretofore.
To appreciate the nuanced improvements described and claimed herein, it is first helpful to set the stage for those improvements by returning to the basics. In that regard, a loudspeaker is device that utilizes an electrical audio signal input to reciprocally drive controlled movement of ambient air to produce sound. The most common form of loudspeaker uses a paper cone supporting an electrical voice coil acting on a permanent magnet. In order to generate the wide range of frequencies necessary to reflect realistic sound, many speaker systems use multiple drivers each covering part of the range of frequencies desired from high to low levels. Ordinary listeners will recognize the driver names of subwoofers for very low frequencies, woofers for low frequencies, mid-range for middle frequencies, tweeters for high frequencies, and where desired, supertweeters for even higher frequencies.
Although different types of speaker drivers exist, one common type of driver employs a magnet surrounding an electrical voice coil to transform electrical input into a mechanical reciprocating motion of the voice coil that drives a diaphragm via a stiffly supported but lightweight carrier. As the voice coil carrier is driven in its reciprocating motion swiftly and repeatedly, the interconnected diaphragm moves with it, creating undulating sound waves perceived by the listeners as audio. The diaphragm is commonly recognized as the “cone” in a traditional mid-range or woofer speaker, or the “dome” of a tweeter design. The focus of the invention described and claimed herein is less on the driver system and more on the arrangement of the diaphragm and associated supports, but driver systems are well understood by the persons of ordinary skill in the art of speaker design.
With regard to diaphragms, more detail is warranted here for context. As indicated, diaphragms are usually constructed with a cone- or dome-shaped profile using one of various types of materials. Traditional diaphragms were made of paper or plastic, with the choice of material and design reflecting a balance of factors. For one, the diaphragm must be able to withstand the forces associated with driving it quickly and repeatedly in a reciprocating motion against the ambient air pressure. So the material must be rigid, but of not too much mass to require a large amount of energy to drive the diaphragm. For another, the diaphragm must be configured and supported so as to be appropriately damped against sustained vibrations due to its resonance frequency once the signal discontinues. To accommodate the competing designs, some speaker diaphragms today consist of a composite material such as cellulose paper embedded with other fibrous or rigid materials, such as carbon fiber, Kevlar, glass, hemp or bamboo fibers. Others employ a honeycomb sandwich construction, or reflect a laminate of differing materials that combine strong, stiff and lightweight materials into the diaphragm.
In any case, the diaphragm is typically supported with primary and secondary support members that permit the desired reciprocating travel in response to signal input while dampening post-signal vibrations. The primary support member maintains the diaphragm in a centered and suspended position above the driver, while the secondary support centers and aligns the voice coil carrier that is connected to the diaphragm and serves to restore the voice coil and the diaphragm to a neutral position after moving.
Sound wave generation and control is tricky because, as one can visualize by casting several objects into the water at one time, waves generated by a single source necessarily interfere with waves generated by other sources. Knowing that waves propagate radially outward from the source, the design of loudspeaker systems take into consideration how each speaker (i.e., individual source of acoustic waves), will interact with other near-by speakers in producing enjoyable audio. Minimizing the distortion of one set of waves by the propagation of an adjacent set of waves drives many high-performance speaker system designs. Of course, one solution is to space individually-driven speakers apart a sufficient distance. A recognized counterbalance to that spacing, however, is the competing desire to simulate a wide range of sound frequencies coming from a single source, which produces a more realistic audio output.
One theory espoused by some audiophiles is that a single source of audio covering the gamut of desired frequencies can generate more enjoyable sound. Based upon this theory, co-axial, and in some cases tri-axial, speakers have been developed to simulate single source sound. A co-axial speaker combines two concentrically-positioned drivers with, for example, a tweeter speaker in the middle surrounded by a mid-range or woofer speaker, both within a single frame or housing. Not surprisingly, co-axial speakers must be designed in a way to address the resultant wave distortion from having overlapping acoustic sources co-axially aligned.
At least one attempt to configure a co-axial speaker in a manner to reduce wave distortion between the central and outer driven diaphragms is embodied by the Thiel CS3.7 speaker system out in the market. With this system, the CS3.7 presents a lower-profile surface to the listener than what a traditional cone-shaped diaphragm presents. However, in doing so, the CS3.7 does not adequately provide a balance between reduced profile and clarity of sound because it employs a mid-range diaphragm that is configured with an radially-projecting corrugated profile that undermines to some degree what otherwise might afford significant reduction in wave distortion. The purpose of the corrugation is ostensibly to maintain sufficient stiffness while having a relatively low mass to withstand the forces of being driven in a reciprocating manner under dampening constraints. But the very solution the CS3.7 attempts to provide is essentially why it fails to achieve the desired balance. That is because the corrugations present obstacles to the acoustic wave output of the centrally-positioned tweeter diaphragm, reducing the benefits otherwise presented with a lower-profile wave guide.